The present invention relates to electrochromic devices which have an extensive use varied from transmission-type devices such as smart windows, reflective-type devices such as antiglare mirrors for automobiles, reflective-type devices such as decorative mirrors to displays.
A method of forming a chromogenic layer for an electrochromic device such as smart windows is known from Japanese Laid-Open Patent Publication No. 63-18336 disclosing a method in which a film of chromogenic layer is formed by vacuum-evaporating an electrochromic active substance such as tungsten oxide (WO3) over a transparent electrically conductive film.
However, this method requires techniques carried out under vacuum conditions, which lead to elevated production costs and the requirements of a large-sized vacuum apparatus for the production of an electrochromic device with a large-surface area. Furthermore, there is a problem that the use of tungsten oxide results in an electrochromic device which can exhibit blue color only.
In view of the foregoing, the object of the present invention is to provide an electrochromic device which can be produced with inexpensive chromogenic materials by a simple method and can be changed in color tone.
After an extensive research and study, it was found that an electrochromic device with the following structure can solve the above-mentioned problems.